Housewrap materials are typically attached or secured to the outer surface of framing or sheathing in the walls of buildings, especially in cold climates. Housewrap materials must be permeable to water vapor to allow water vapor to escape from the wall to which the film is secured to prevent, for example, water damage to the walls and/or growth of molds or the like. On the other hand, the housewrap materials should be sufficiently impermeable to air and liquids to insulate the wall against wind and rain or other precipitation. Further, housewrap materials should have adequate tensile and physical properties such as break strength, elongation, tear strength, shrinkage and puncture strength to avoid damage during installation and to facilitate durability.
To provide housewrap materials and other breathable materials suitable for construction and similar heavy duty use with sufficient strength and toughness, it is often desirable to use strong and/or tough nonwoven and/or woven materials. Typically, such nonwoven and woven materials exhibit relatively low elongation capabilities, i.e., less than about 30% elongation, which can limit the techniques employed to form composite materials therefrom.
The Sheth U.S. Pat. No. 4,929,303 discloses composite breathable housewrap materials which comprise a breathable film formed of linear low density polyethylene and a nonwoven fabric formed of cross-laminated fibers. The breathable film is formed by cast extruding a precursor film onto a roller, stretching the precursor film to impart permeability, heating the nonwoven fabric, and pressing the heated fabric to the film to bond the fabric and the breathable film. Owing to these successive processing steps, the manufacture of the disclosed housewrap materials can be somewhat cumbersome and expensive.
Accordingly, a need exists for improved breathable materials, including those which may employ relatively strong or tough nonwoven layers, and to methods for facilitating the manufacture of such materials.